textproduct: Albany

WHAT HAS CHANGED

Small hail and gusty winds were added for the isolated to scattered thunderstorms this afternoon.

Patchy fog was expanded across eastern NY and western New England tonight especially in the major river valleys with some recent wet ground and the radiational cooling expected with the surface high building in. Low temps were lowered closer to the MAVMOS numbers for Saturday morning.

Lowered dewpoints into the mid 40s to the mid/upper 50s on Saturday with the drier air mass building in, as the NBM numbers were too high in the mid 50s to lower 60s in the valleys.

Slowed down the timing for higher PoPs for showers and isolated thunderstorms until the mid to late afternoon on Sunday. WPC maintains a Marginal Risk (Level 1 of 4) for Excessive Rainfall for Sunday into Sunday night for most of the region, but increased the I-84 corridor near southern Ulster, southern Dutchess and southern Litchfield County to a (Level 2 of 4) Slight Risk.

KEY MESSAGES

1) Isolated to scattered showers and thunderstorms will impact the region this afternoon and their is a Marginal Risk (Level 1 of 5) a few storms may become severe.

2) Cooler temps and drier weather begin the weekend, but then the next system brings a widespread rainfall with showers and some thunderstorms Sunday afternoon into early Monday.

DISCUSSION

KEY MESSAGE 1...

A mid-level short-wave in the northwest flow aloft over the Northeast will bring isolated to scattered showers and thunderstorms this afternoon. Isolated to scattered showers have already begun to increase across the region by 18Z. The 500 hPa temp on the 12Z KALY sounding was -11C. Mid-level lapse rates remain weak at less than 6C/km. The surface dewpoints are in the 50s to lower 60s with spotty mid 60s closer to the mid Hudson Valley in the NYS mesonet. Low-level lapse rates are steep in the 8-9C/km range. The latest SPC RAP Meso-analysis indicates MLCAPE mainly 250 J/kg or less, and we may see an increase to 250-500 J/kg. The SBCAPE values are generally 500 J/kg or less. Some of the CAMs show an increase to 500-100 J/kg of SBCAPE, but based on the present dewpoints instability is limited. However, the 0-6 km bulk shear continues to 50-60 KT with strongest winds of 50-66 KT close to 500 hPa. Some low-topped thunderstorms are possible with gusty winds and small hail. We can not rule out an isolated severe storm with damaging winds, but the limited instability should inhibit updrafts from getting tall enough for a widespread severe threat. SPC placed the entire area in a Marginal Risk (Level 1 of 5) for an isolated severe threat this afternoon. PWATs are 1-1.25" and the strong flow aloft should limit any hydro threat.

The showers and thunderstorms should diminish quickly in the late afternoon/early evening with the short-wave passage and the loss of the diurnal heating. Patchy fog will likely form in the major valleys with clearing skies and recent wet ground in spots with light to calm winds with the ridge moving in from southeast Canada.

KEY MESSAGE 2...

High pressure will build in from southeast Ontario and southwest Quebec for Saturday. After morning radiational fog burns off, expect temps to rise from the 40s and mid 50s. Low temp readings around 40F are possible in the southwest Adirondacks Saturday morning. Expect mostly sunny conditons and dry weather during the day due to the strong subsidence from the surface high. Max temps will run slightly cooler than normal for mid-August with highs in the upper 70s to around 80F in the valleys and mid 60s to mid 70s over the hills and mtns. It will be very comfortable and the dry and less humid air mass with dewpoints in the mid 40s to 50s. The surface anticyclone will move east of the region to near southeast New England by Sunday morning. Another cool morning is expected with lows in the mid 40s to mid 50s again with some mid and high clouds increasing from the south and west ahead of a warm front and low pressure system approaching from the Great Lakes Region. Some localized patchy to areas of fog will be possible near the CT River Valley near southeast VT and also the Lake George/Glens Falls area.

The 2nd half of the weekend begins dry, but heights begin to fall with the mid-level flow becoming nearly zonal. The low to mid level warm advection increases ahead of the warm front for showers to increase west of the Hudson River Valley/I-87 corridor in the late morning into the early afternoon, and then increasing to likely to categorical PoPs (55-80%) by the late afternoon to early evening, as the low pressure system and mid and upper level short-wave approaches.

PWATS rise above normal and the low-level moisture increases. Some elevated instability will in place for a slight chance of thunderstorms Sun pm into Sun night. The latest 24-hr NBM probabilities for >1" of rainfall for the period ending 8 am/Monday are 25-60%. The 2" probabilities are generally under 20% for the same time period. A secondary low or weak wave may form along the front continuing the rain well into Monday morning for locations south and east of Albany. However, the system looks progressive on the ensembles and deterministic guidance with 0.50-1.00" of rainfall with some 1-2" amounts along the southwest slopes of the Adirondacks, eastern Catskills, and possibly portions of western New England. WPC has kept a Marginal Risk (Level 1 of 4) across most of the region for an isolated flash flood threat, though they did place the southern extreme of the forecast area in a Slight Risk (Level 2 of 4) which is near the I-84 corridor, where soils are wetter/more saturated recently. We will continue to monitor this event, as it appears ponding of water on roadways and poor drainage flooding of low-lying or urban areas would be the main issues, unless high rainfall rates are achieved. Drier weather returns Monday afternoon through Tuesday with seasonable temps, before another system brings some showers and thunderstorms late Wed into Thu.

AVIATION /18Z FRIDAY THROUGH WEDNESDAY/

Through 18Z Saturday... VFR conditions will prevail across all terminals for the majority of this TAF period, with light northerly winds and some low-to-mid level cigs building in across the region. There is a chance for isolated showers/thunderstorms throughout this afternoon and evening, reflected by PROB30 groups at all terminals, which could bring variable and gusty winds with brief vis drops to MVFR. This threat should clear out by 00Z, giving way to calm winds with a few lingering low and high clouds. Given the calm winds and mostly clear skies, there is potential for the development of some radiational mist/fog in the early morning hours of Saturday, mainly for KGFL, KALB, and KPSF. This could bring periods of IFR vis to these terminals throughout the morning. Any mist/fog that develops should burn off by 12Z-13Z, bringing back VFR conditions at all terminals with light northerly winds returning with primarily FEW-SCT low and high clouds across the region.

Outlook...

Saturday Night: No Operational Impact. NO SIG WX. Sunday: High Operational Impact. Breezy. Likely SHRA...TSRA. Sunday Night: High Operational Impact. Breezy. Definite SHRA...TSRA. Monday: Low Operational Impact. Slight Chance of SHRA. Monday Night: No Operational Impact. NO SIG WX. Tuesday: No Operational Impact. NO SIG WX. Tuesday Night: No Operational Impact. NO SIG WX. Wednesday: Low Operational Impact. Slight Chance of SHRA...TSRA.

ALY WATCHES/WARNINGS/ADVISORIES

CT...None. NY...None. MA...None. VT...None.